A friend of mine is running NOD32 v2.70.32 on WinXP Pro SP2 and this week he could not boot his machine one morning but got a msg saying something about "isass.exe", he couldn't even boot the machine into safe mode it just kept on repeatedly going back the menu options where Safe Mode can be selected, no menu item would let him boot the machine at all.

It is a brand new machine of just 2mths.

Any suggestions as to why NOD32 missed the Trojan as the database was up to date prior to booting the PC on the morning this took place?